Vacuuming Building Cavities to Screen for Hidden Mold: Guide to Good Practices InspectAPedia® -
Field testing vacuum tests of building cavities to check for mold contamination
Does vacuuming wall or ceiling cavities for mold produce reliable results?
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This article explains the advantages and shortcomings of using vacuum cassettes or spore traps to collect mold test samples (or other dust or particle samples) from building wall and ceiling cavities. In this article series discuss the validity of nearly all of the popular mold testing methods currently in use, pointing out the strengths and weakness of each approach to mold sampling in the indoor environment, beginning with air sampling for airborne mold levels indoors. Because mold test validity and mold test accuracy are often confused, readers should also see ACCURACY OF VARIOUS MOLD TEST METHODS. People who need to conduct mold inspection and testing indoors should see MOLD TEST PROCEDURES and TECHNICAL & LAB PROCEDURES.
Our MOLD INFORMATION CENTER includes more broad discussions of the overall approach to building investigation, as do many expert references cited at that web. For a more
comprehensive collection information about mold test methods see INDOOR AIR QUALITY METHODS COMPARED.
For more on "mold classes" (Cosmetic mold vs. allergenic mold vs. toxic or pathogenic mold) see MOLD CLASSES, HAZARD LEVELS and more references such as a Mold Action Guide are at the end of this document.
Validity/Accuracy of Vacuuming Building Cavities for a Hidden Mold Screen
15th Annual North Carolina/South Carolina
Environmental Information Association Technical Conference
Myrtle Beach, SC
Daniel Friedman 23 September 2005, Updated 4/14/2009
Vacuuming building cavities is a popular screening practice to look for mold
reservoirs. The investigator is trying to explore wall cavities while doing
minimal or no visible damage.
A wall-check™ system has been marketed for this
purpose and several manufacturers have coped the basic idea: a receiving
Air-o-Cel™ or MCE filter cassette is attached at its inlet side to a tube which
is inserted as a probe into a wall cavity, permitting creation of only a small
hole. The outlet or pump side of the test device is connected to a pump and
operated, typically at 15 lpm. Where we have tested this method we have
experimented with both passive collection (what most investigators use) or
aggressive collection (banging on the wall/ceiling at various points to attempt
to dislodge and stir particles).
Short duration samples, 1-2 minutes using an Air-o-Cell ™ permit a
comparatively large number of samples to be collected in a reasonably short
interval. Long duration samples, perhaps for up to two hours, are collected
using an MCE filter cassette.
Wall Cavity Vacuuming - Found Ineffective
Working with Louis Relle, a Louisiana mold remediation expert on a New
Orleans Building which was to be demolished we collected wall-check samples from every suspect Building cavity.
When the
building interior surfaces were demolished we then performed a visual inspection and collected bulk surface samples using tape.The wall check samples were
completely unable to detect large and significant mold contamination in the cavities of this building.
We postulate that
even with mechanical agitation (banging on the wall during wall check sampling) the flow rate of the sampling method does
not move enough air to reliably pick up surface contamination unless the mold genera/species happens to be at a
particularly high state of active sporulation. The tool remains in the professional's arsenal, to be used with
discretion.
Shortcomings of vacuuming building cavities through a tube but our testing
strongly suggests that this method is very unreliable for characterizing wall
contents. We do not believe that enough air movement is created in the wall
cavity (sucking any lpm flow through a small diameter tube) to reliably collect
what could be a severe mold reservoir that happens not to be right next to the
probe. Further if the cavity is insulated there will be virtually no air or
particle movement except from very close to the probe.
What should we make of wall vacuum test results done without
other inspection and testing?
Wall
cavity vacuum tests, depending on how and when they are performed, can be
like searching for a needle in a haystack while looking through a straw: if you
find evidence of a problem you're lucky. But if you don't find evidence, when
using a very limited-scope method, that doesn't mean that a problem is not
there.
Our photo, left, is not showing the wall-check vacuum method that relies on vacuuming into a cassette through a hole in the wall. Instead, here we have pulled loose paneling and have inserted our spore trap cassette into the cavity.
This position combined with aggressive sampling by banging on the wall paneling with a flashlight is more likely to collect problem particles if they are present close to the point of vacuum cassette insertion into the wall. But even this approach is not a reliable characterization of mold risk in the building. And it is not looking into the wall cavity itself - rather we are looking at the two surfaces behind the paneling.
Short vacuum pump duration for microscopic examination (to avoid
sample overload, e.g. 2-=3 minutes on an Air-O-Cell) does not move enough air
to reliably find what may be in the wall
cavity. An experiment done with Louis Relle in New Orleans LA demonstrated that
wall-vac tests found less than 10% of large problem mold cavities that could
be discovered by cutting drywall openings in a building.
Our photo (left) shows a short-duration but larger surface area or wall opening vacuuming system invented and tested by the author - it did not provide useful results.
Longer vacuum pump duration samples for viable sampling (2 hours
into an MCE cassette for culturing) still may not move enough air to sample
through a cavity, particularly if the cavity is insulated. Further, two-hour
samples means that most-likely very few sample points were collected, making
the inspection scope extremely limited and thus overall confidence in the
accuracy of the picture of the building lower.
Consider that the popularly-marketed version of this wall cavity vacuuming approach
to test for hidden mold contamination in buildings relies on culture of the sample. Did you know that only about 10% of molds grow
in any culture at all? You're 90% uncertain of the accuracy of the test at the
outset. One can't be sure that the mold that grew in the culture represents the
dominant problem mold or whether it's just a low-occurrence (in the building) spore
that liked the media (in the culture). We like cultures for further
genera/species identification of samples but we are nervous about relying on them
to tell me if the building has a problem or not.
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Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
Allergen Tests in Buildings advice about how to test, what to look for, in evaluating the level of dog, cat, or other animal allergens in a building
"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Animal Allergens: Dog, Cat, and Other Animal Dander - Cleanup & Prevention Information for Asthmatics and regarding Indoor Air Quality.
Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
Rodent control issues, including dander, fecal, and urine contamination of Buildings and Building insulation are discussed at our
Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon)
Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
"Disease Prevention in Home Vegetable Gardens,"
Patricia Donald,
Department of Plant Microbiology and Pathology,
Lewis Jett
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold
Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold
cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.
Ozone Warnings - Use of Ozone as a "mold"
remedy is ineffective and may be dangerous.
Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the
areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic
bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details
see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings,
and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating
the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing
rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some
help from a licensed pest control expert.
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